Advanced

A Study and Modelling of Chaff Clouds Affected by Wing-Tip Vortices

Persson, Jonathan LU and Warlin, Jakob (2019) EITM01 20191
Department of Electrical and Information Technology
Abstract
Chaff are thin strips of either metal or metal coated fibres used as countermeasures
against radar. When deployed from an airplane, the turbulence and wing-tip
vortices from the airplane disperse the chaff into a chaff cloud, which may appear
as a false target and jam the radar. A Doppler radar is able to discriminate
between chaff and targets by using the Doppler spectra. Such signal processing
methods already exist, and are evaluated with real data from flight tests. However,
flight tests are expensive and a way to simulate a chaff cloud would therefore be
preferred.

This master thesis was a pilot study which investigated the current knowledge
of chaff modelling with wing-tip vortices. Two models were created, an individual
chaff model... (More)
Chaff are thin strips of either metal or metal coated fibres used as countermeasures
against radar. When deployed from an airplane, the turbulence and wing-tip
vortices from the airplane disperse the chaff into a chaff cloud, which may appear
as a false target and jam the radar. A Doppler radar is able to discriminate
between chaff and targets by using the Doppler spectra. Such signal processing
methods already exist, and are evaluated with real data from flight tests. However,
flight tests are expensive and a way to simulate a chaff cloud would therefore be
preferred.

This master thesis was a pilot study which investigated the current knowledge
of chaff modelling with wing-tip vortices. Two models were created, an individual
chaff model and a Gaussian model. The individual chaff model was based on
physical phenomena and simulated the effect of the wing-tip vortices on a chaff
cloud. The Gaussian model was based on distributions and trends, and should
be adjusted to real data. Due to confidentiality, real data could not be used.
Instead, two flight scenarios were used to evaluate the individual chaff model. The
Gaussian model was then adapted to these results.

The individual chaff model was able to simulate two separate flight scenarios
with distinguishable results. Moreover, the model also showed some promising
results when compared to RCS trends from previous published models. Statistical
characteristics of the RCS values agreed with Swerling models. The RCS values
were however low, due to insufficient diffusion simulation. This also resulted in
inaccurately simulated cloud sizes. The Gaussian model was able to mimic the
behaviour of the individual chaff model with reduced run-time.

More work is necessary to fully understand the behaviour of wing-tip vortices,
as well as the ability to use real data for evaluation. Theoretical work and more
advanced simulation methods are required to understand and model the behaviour
properly. (Less)
Please use this url to cite or link to this publication:
author
Persson, Jonathan LU and Warlin, Jakob
supervisor
organization
course
EITM01 20191
year
type
H2 - Master's Degree (Two Years)
subject
keywords
chaff study modelling aerodynamics wing-tip vortices
report number
LU/LTH-EIT 2019-695
language
English
id
8977666
date added to LUP
2019-06-11 15:04:21
date last changed
2019-06-11 15:04:21
@misc{8977666,
  abstract     = {Chaff are thin strips of either metal or metal coated fibres used as countermeasures
against radar. When deployed from an airplane, the turbulence and wing-tip
vortices from the airplane disperse the chaff into a chaff cloud, which may appear
as a false target and jam the radar. A Doppler radar is able to discriminate
between chaff and targets by using the Doppler spectra. Such signal processing
methods already exist, and are evaluated with real data from flight tests. However,
flight tests are expensive and a way to simulate a chaff cloud would therefore be
preferred.

This master thesis was a pilot study which investigated the current knowledge
of chaff modelling with wing-tip vortices. Two models were created, an individual
chaff model and a Gaussian model. The individual chaff model was based on
physical phenomena and simulated the effect of the wing-tip vortices on a chaff
cloud. The Gaussian model was based on distributions and trends, and should
be adjusted to real data. Due to confidentiality, real data could not be used.
Instead, two flight scenarios were used to evaluate the individual chaff model. The
Gaussian model was then adapted to these results.

The individual chaff model was able to simulate two separate flight scenarios
with distinguishable results. Moreover, the model also showed some promising
results when compared to RCS trends from previous published models. Statistical
characteristics of the RCS values agreed with Swerling models. The RCS values
were however low, due to insufficient diffusion simulation. This also resulted in
inaccurately simulated cloud sizes. The Gaussian model was able to mimic the
behaviour of the individual chaff model with reduced run-time.

More work is necessary to fully understand the behaviour of wing-tip vortices,
as well as the ability to use real data for evaluation. Theoretical work and more
advanced simulation methods are required to understand and model the behaviour
properly.},
  author       = {Persson, Jonathan and Warlin, Jakob},
  keyword      = {chaff study modelling aerodynamics wing-tip vortices},
  language     = {eng},
  note         = {Student Paper},
  title        = {A Study and Modelling of Chaff Clouds Affected by Wing-Tip Vortices},
  year         = {2019},
}